The sol-gel derived ceramic materials have many applications in various fields. Bioceramics is one of the most promising and interesting fields that still need much development work for optimizing the properties of the material in the biological environment. The sol-gel process starting from a liquid phase enables an easy control of the pore structure of the material and an introduction of other components in different kinds of composites, especially, in the case of silica-based materials. The processing of the sol-gel derived silica fibres is known, and the main parameters controlling the process are the functionality of the silica precursors, or the degree of branching of the silica clusters. The latter critically affects the spinnability and has commonly been characterised by rheological measurements.
Fibres have traditionally been used to improve mechanical properties of materials. In the case of the sol-gel derived silica fibres, there are two main parameters that determine the fibre bulk structure. Heat treatment of the fibres is one way to condense the bulk structure. Depending on the application of the sol-gel derived biodegradable silica fibres, the balance between mechanical properties and biodegradation may vary. For example, the mechanical properties are of minor importance when the silica fibre is used as a drug delivery device in a soft tissue. However, the mechanical properties have to be good enough to further process the obtained fibres to a desired form after spinning. The biodegradation of the silica fibre decreases remarkably after heat-treatment at high temperatures simultaneously as the mechanical properties become better.
International patent publication No. WO 97/45367 discusses sol-gel produced silica-xerogel materials. Patent publication DE 19609551 discusses silica fibers obtained by drawing them from a specific spinning composition. Neither of the patent publications teaches or suggests a controllably biodgradable silica fibre, a delivery device, or a pharmaceutical composition according to the invention or methods for preparing or using the same. Further, neither of the patent publications teaches or suggests a method according to the invention for controlling the biodegradation of a silica fibre.